ANALYSIS ON THE LONG TERM COOLING EFFECT OF URBAN GREEN AREA ON URBAN CLIMATE

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Urban green area is considered as a cool island in an urban heat island. We made micrometeorological investigation at Shinjuku Gyoen Park, which is one of large green areas in the center of Tokyo area. We measured special distributions of temperature and humidity, profiles of ground temperature and surface temperature by infra-red thermography. As a result, cool island effect of the park is obvious and cool air flows to the surrounding urban area. At the center of the park, low soil temperature was observed, which indicates low temperature at the park for long term trend. Heat balance calculations indicate that high sensible heat flux from the surrounding urban area and high latent heat flux from the park.A two dimensional k-ε two equation model was used with the equations of temperature and normalized humidity to analyze the thermal effect of urban green areas. The relation between the scale of an urban green area and its influence and the relation between the interval of an urban green area and its influence were analyzed.From the distribution of temperature and normalized humidity, it is observed that a green area of larger scale influences a higher area. From the distribution of diffusivity, a large value was observed at the transition area from green area to urban area and this tendency was the same in the case of two green areas.