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

城市绿地被认为是城市热岛中的凉岛。我们在新宿公园进行了微气象调查，这是东京地区中心的大型绿地之一。我们用红外热像仪测量了特殊的温湿度分布、地面温度和地表温度的分布。结果表明，公园的凉岛效应明显，冷空气流向周边城区。园区中心地温偏低，预示着园区气温长期偏低趋势。热平衡计算表明，城市周边区域的显热通量较高，公园的潜热通量较大。采用二维k-ε两方程模型，结合温度和归一化湿度方程，对城市绿地的热效应进行了分析。分析了城市绿地规模与其影响的关系以及城市绿地间隔与其影响的关系，从温度和归一化湿度的分布来看，较大规模的绿地影响较高的面积。从扩散系数的分布来看，从绿地到城市的过渡区有一个很大的值，两个绿地的情况也是如此。

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.