Abstract
Heat islands of the cities in the Kanto Plain are recognized in the LANDSAT Thematic Mapper (TM) channel 6 image in assending mode (Path : 206/Row : 209) which was taken in 14/Aug./1984. The purpose of this study is to clarify the relationship betmeen the heat island intensity and the scale of urban area using the satellite image.
TM image is superimposed on the land use mesh map (KS202) in the Digital National Land Information of the Geographic Survey Institute, Japan. As a measure of the scale of the urban area, four indices are selected. They are the population density, population and the area of the Densely Inhabited District (DID), and the area of building site A (category 7) in the mesh map. Heat island intensity is defined as maximun difference in the digital number (DN) of the TM channel 6 between the building site A (category 7) and the paddy field (category 1), which is selected as a representative of suburban area. By using the mesh map as a mask on the TM image, heat island intensity is calculated for 35 cities in the Kanto Plain.
Heat island intensity increases with the increase in the scale of urban area. It is mutually related to the area of urban area rather than the population in the urban area. In the city surrounded by active vegetation, such as paddy in summer, heat island intensity becomes larger than that of the city surrounded by a small amount of vegetation, even though the scale of urban area are the same. Heat island intensity is not the index of the urban area itself, but the index of the area which includes the urban and surrounding suburban area.
Comparison of the thermal image with the Normalized Vegetation Index (NVI) image, which is processed from the MSS data in 31/Jul./1984, reveals the close relationship between the observed brightness temperature and the vegetation. Digital number in TM channel 6 decreases with the increase in NVI. It suggests that the vegetation lower the temperature of the terrain, and the distribution of vegetation strongly controls the thermal environment of the terrain.
