STUDY ON URBAN HEAT ISLANDS IN TOKYO METROPOLITAN AREA USING A METEOROLOGICAL MESOSCALE MODEL INCORPORATING AN URBAN CANOPY MODEL

The temperature increase due to urbanization, i.e. urban heat island, is getting very serious in Japanese cities. Urban heat island phenomena are analyzed by many researchers . Three-dimensional meteorological mesoscale model is often used to solve the mechanism of urban heat island[1,2]. On the meso-scale analysis, one-dimensional heat balance model is used mainly as ground boundary conditions. However it is necessary to include the effect of building canopy exactly in order to analyze thermal environment at pedestrian level in urban area. On the other hand, one-dimensional urban canopy model is also used commonly to analyze urban climate[3,4]. This model can predict thermal environment at pedestrian level easily. However it is impossible to analyze three-dimensional property of climate including effects of advection and diffusion by this model due to the assumption of horizontally homogeneous flow and temperature field. In this study, meteorological meso-scale model based on Mellor-Yamada model level 2.5 [5] is incorporated with the urban canopy model proposed by Kondo et.al [3] as the boundary conditions. The 3D detailed digital map information system is also utilized for representing the property of the real building canopy such as building hight and building width. Such shapes of building complex are measured by airbone laser scaner. The urban thermal environment in Tokyo metropolitan area is analyzed by means of this new method developed here. The results of the new method developed here show good agreement with the observation compared to those of the conventional method.

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