Shuji Yamashita

On relationships between heat island and sky view factor in the cities of Tama River basin, Japan

Abstract This study aims at firstly identifying heat island phenomena, secondly relating heat island intensity to city size, and thirdly providing basic urban climatic information to city planners or ordinary citizens. Horizontal distributions of dry- and wet-bulb temperature were measured seasonally in small to medium sized cities by mobile observers. Also, at a fixed station, wind speed and wind direction in addition to temperature were observed. The cities selected for this were Tachikawa, Fuchu, Fussa, Higashimurayama and Akikawa, which are suburban cities in the W part of Tokyo. This area is part of the middle basin of Tama River. Observations were made both during the day and at night in winter (February and December), spring (March and May), summer (July and August) and autumn (October and November) over a period of maximum duration of 1.5 h. In all cities heat islands were observed to develop to some extent. Their intensities were largely dependent on weather conditions. Cities in Japan have been growing rapidly and randomly, and merging into neighbouring small cities or towns. This expansion is called sprawl. Due to these factors it is very difficult to determine a good indicator of city sizes, i.e. population or DID (Densely Inhabited District) population does not represent the effect of city size on heat island intensity. Sky view factors were determined using a fish-eye lens and a calculation chart. We therefore examined central urban area and sky view factor as a cause factor for heat islands. It is concluded that sky view factor is a very useful indicator of the effect of urbanization on heat island intensity.

Detailed structure of heat island phenomena from moving observations from electric tram-cars in Metropolitan Tokyo

In this study, the detailed horizontal structure, i.e. cliffs and plateaux of the heat island of the Metropolitan Tokyo area is investigated. According to Oke (1977), cliff is steep temperature gradient at the rural/urban boundary and plateau is a steady but weaker horizontal gradient of increasing temperature towards the city center. However, these features are not always evident, e.g. large city like Tokyo. To elucidate such aspects, moving observations of the horizontal distribution of air temperature from electric trains of the transportation network of Metropolitan Tokyo during late evening or early morning were thus conducted. In total, 16 railroad lines were used for the moving observations. The observations were done in two phases for sectional and horizontal distributions. Results show that three cliffs exist in the heat island of Metropolitan Tokyo, although the location of these cliffs should be taken into consideration for urban planning or urban redevelopment.

A comparative study of turbidity in an urban and a rural environment at Toronto

Abstract Values of Linkes turbidity factor in Toronto and at nearby rural locations were computed from the measurements of global and diffuse sky solar radiation on cloudless days. The turbidity factor was larger in the city than in the rural area through the year except for some time in the summer. A comparison of turbidity factor for the same optical air masses and wind directions was also made.

Some studies on the earth's surface conditions relating to the urban heat island

Abstract The recent studies of the earths surface conditions relating to heat islands in Japan are presented from geographical viewpoints as an activity of the Association of Japanese Geographers. Urban climate is defined as the result of urbanization, which is expressed as concentration of population, modification of earths surface constituent materials, and expansion of living space onto and under the ground. These bring about changes in morphological and physical features of the urban surface, and its energetic conditions, which consequently and unintentionally modify radiation, heat and water balance in urban areas. Some estimations of urban surface conditions are at first explained. Surface conditions treated in this study are morphology of urban surface (mainly building height), roughness, sky view and energy consumption. Next, the relationships were considered between air temperature and surface morphology, heat island intensity and population, population and sky view factor, respectively. Finally the regional differences in heat islands were discussed, and the necessity of urban climate studies to ameliorate human and global conditions.