Abstract
The formation of a city itself brings about the urbanized climate, which is called urban one. The most typical example of which is a heat island phenomenon. Urbanization may be defined as a process of growth of a city, and expressed with concentration of population, artificialization of the urban surfaces and expansion of living space onto and into the ground. These are the factors which may modify radiation balance, heat budget and water balance in an urban area. However, the cities of Japan are quite different from foreign ones from the view points of morphological features and constituent materials. At first the characteristics of a heat island in Japan is noted, and then its formative factors are considered. The most notable feature of a heat island in Japan is that isothermal lines are not so dense around the boundary of a city. This may be due to the sprawl-like expansion of a Japanese city. Next, its formative factors are considered such as height of buildings, area of nonpermeable surface, roughness parameter and soil moisture content. These factors are rather well correlated with heat island intensity. The cities investigated are Tokyo, Kichijoji, Ohgaki and Kawagoe.
