Abstract
In this study, the relationship between urban size and the heat island intensity is analysed by using meso scale Weather Research & Forecasting (WRF) model, in three cities with different sizes (Tokyo, Osaka and Nagoya area). Since the urban area is extended to inland where is potentially likely to be higher air temperature in Tokyo area, higher air temperature is recognized in inland area. When urban area is increased, higher air temperature area is increased in inland area, since the urban area is likely to extend to inland area. Therefore, indirect relationship is confirmed between the spatial average air temperature in urban area and the urban size.
If the urban form such as building coverage ratio and building height is the same, air temperature rise in urban area is not confirmed when urban size is expanded. Therefore, it is considered that there is no relationship between urban size and the heat island intensity. However, the spatial average air temperature in urban area rises when urban size is expanded, since higher air temperature area increases in inland. In the case of calculating the heat island intensity using the spatial average temperature in urban area, the heat island intensity is related to urban size.
When calculating the heat island intensity by a conventional manner, if selecting a representative temperature in urban area near the coast or inland, the heat island intensity varies significantly. Therefore, the heat island intensity should be calculated based on air temperature distribution which was gained by repeatedly movement measurements intended for several urban areas as performed Sakakibara et al. or by meso scale model as in the present study.
