Effects of Roughness Parameter due to Buildings and Thermal Property of Construction Materials on Temperature Distribution in a Housing Complex

Abstract

Among the formative factors of the urban climate, roughness due to buildings and the thermal property of construction materials have a great influence on the appearance of the urban heat island. In the present paper, the influence of these factors on the heat island is discussed based on the observation data in and around the Homi housing complex in Toyota City, central part of Japan. Special attentions have been paid on the roughness parameter defined by Lettau (1969) and the thermal property of the construction materials as the surface condition in the housing complex to explain the distribution of air temperature. Results of this study can be summarized as follows : Centers of high temperature area in the Homi housing complex are likely to appear in the area with large roughness parameter. Though the heat island intensity enlarges due to the increase in the roughness parameter, the heat island intensity indicates a nearly constant value in the range of particulaly high roughness parameter. Moreover, 1/cρ√<κ> , which is a combined parameter of the specific heat, the density and the thermal conductivity, shows negative correlation with the heat island intensity. These relationships are more marked during the nighttime and the early morning, when the radiation cooling is active, than the daytime. A large quantity of absorbed heat into buildings during the daytime should contribute to the maintenance of high temperature condition during the nighttime.