Estimation of a potential space for the rooftop greening in the tokyo metropolitan region

A potential space for the rooftop greening in the Tokyo metropolitan region was estimated by analyzing the polygon data of buildings and the digital areal photographs of the Shinjuku ward. The usage of buildings and the number of floors in buildings in the 23 wards of the Tokyo metropolitan region were almost same as those in the Shinjuku ward, therefore, a ratio of the potential space for the rooftop greening in the Shinjuku ward was estimated by a random sampling method at first. Then, a potential space for the rooftop greening in the 23 wards was estimated, based on a result of the Shinjuku ward. The ratio of the potential space for the rooftop greening varied from 37.8% to 93.6%, depending on the usage of buildings and the number of floors in buildings. By then, the invariable ratio of 86% had been suggested by the Ministry of Construction (1995), however. the present study manifested that this ratio did not always hold true. The potential space for the rooftop greening in the 23 wards was estimated at 5,069 ha, which was as large as about 8% of the 23 wards\u27 area. In comparison with the ratios of the potential space for the rooftop greening in low-rise buildings and in medium-rise buildings, those in high-rise buildings and in skyscrapers were smaller. Since the latter buildings directly warm the upper part of the urban atmosphere through the sensible heat flux, the results of the present study can be important when the energy balance of the urban atmosphere is investigated