Numerical Prediction of Heat Island Mitigation Effect on Decrease in Air Temperature in Tokyo

The intensity of urban heat island is known to be stronger as city size (for example population of city) (Oke, 1973). In Tokyo 23 wards (hereinafter referred to as "Tokyo") with more than eight million people, urban heat island phenomenon is actualized and feared as a factor of increase in heatstroke patients and raising cooling energy consumption in summer. Therefore, Tokyo Metropolitan Government promotes some heat island mitigation measures concerning with urban greening, reducing anthropogenic heat, and so on. In introducing heat island mitigation measures, it is important to grasp these faculties in advance. A three dimensional numerical simulation is thought to be one of the most effective tools for this purpose. In previous studies, three-dimensional numerical simulations have been performed in order to predict the contribution of some influential factors like land coverage or anthropogenic heat to urban heat island (Kimura and Takahashi, 1991). By using a three-dimensional numerical simulation with the horizontal distribution of surface coverage and anthropogenic heat, the effect of mitigation measures on decrease air temperature can be evaluated with their various spatial arrangement patterns in urban area. On the other hand, it is required to pay attention to the adequacy of numerical model by comparing its results with field observation data.