Hydro-meteorological Studies on the Effects of Vegetation (street trees and wall-covering ivies) on the Mitigation of Urban Climate

由于高层建筑和铺砌道路的建设以及绿地和水域的减少，大城市中心地区变得越来越温暖；即“热岛”的形成。为评价植被对城市热环境的影响，开展了三种调查；(1)野外测量；(2)计算机实验（=数值模拟）；(3)分析人造卫星LANDST的遥感数据。(1)在中央大学多摩校区进行了环境测量。测量了由于潜热释放引起的绿色效应对热环境的降温作用。植物冠层的表面温度相对于邻近建筑的墙体温度和铺装道路的温度较低，且与周围气流的湿度和速度的变化无关，冠层表面温度几乎保持不变。测量结果表明，绿色效应受土地利用方式差异的影响较大。(2)应用LES湍流计算模式进行了植被对城市气候影响的数值实验。当阳光反方向照射到建筑物上时，在建筑物的后墙区域会遇到严重的情况，该区域吸收了强烈的日照能量，成为流场的热源。如果将被建筑包围的中心地块由运动场改为森林公园，热环境将得到很大的改善。由于植被的蒸散发作用，使潜热释放出来，缓和了城市热环境，使得比盛行风高7ºC的最高温升几乎被抵消。(3)利用LANDSAT遥感数据估算了区域地面和森林温度分布，揭示了植被对气候减缓的影响。提出了一种估算蒸散速率区域分布的新方法，扩展了互补规则。少

Central regions of big cities are becoming warmer and wamer due to the construction of tall buildings and paved roads and the reduction of green and water area ; i.e.the formation of "HEAT ISLANDS". In order to evaluate the effects of vegetation in the themal environment of urban region, the three kinds of investigation have been performed ; (1) field measurement, (2) cpmputer experiment (=numerical simulation), and (3)analysis or remote-sensing data from a man-made satellite LANDST.(1) Environmental measurement has been carried out at Tama Campus of Chuo University. The temperature decrease in thermal environment by green effect due to latent heat release has been measured. Surface temperature of plant canopy layr was lower compared with the wall temperature of a neighborling building and with temperature of paved road, and was held almost constant level irrespective of the temporal changes in humidity and velocity of surrounding air flow. The measurement shows that the green effect i … More s infulenced by the difference of land utilization.(2) Numerical experiments applying the LES model of turbulence computation were performed for the vegetation effects on urban climate. When the sun light sheds on buildings from the reversed direction to wind flow, severe circumstance is encounted in the rear wall region of buildings which absorb the strong insolation energy to become the thermal source in the flow field.If the use of central block surrounded by buildings is changed from athletic field to forestry park, the thermal environment is greately improved. The maximum temperature rise amounting to 7ﾟC above that of prevailing wind is almost cancelled, due to the effect of evapotranspiration of vegetation, by which the latent heat is released to mitigate the urban thermal environment.(3) Remotely-sensed data obtained by LANDSAT have been analyzed to estimate the regional temperature distribution of ground and forest, to show the vegetation effects on climate mitigation. A new method has been proposed for estimation the regional distribution of evapotranspiration rate, extending the complementary rule. Less