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

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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