The zero-plane displacement height d was evaluated in downtown Tokyo by the two independent methods of temperature variance and scintillometer heat flux. Regardless of the method, d exceeds the area-weighted average building height. This may be because d, which represents the point of effect for wind drag, is elevated by some tall buildings that jut above others. The areaweighted average building height would then be unsuitable as a geometrical index of urban canopies with large height variations. Thus, the height of the upper envelope of the canopy was proposed as the representative canyon height.

In this paper, results are shown from micro-climatological observations performed in and around a largest green space in central Tokyo, "Imperial Palace", during summer. Its area is 230ha, and it was once the Edo-Castle, then surrounded by a moat.In a clear calm night, the cool air flows out from the Imperial Palace to the surrounding city area gravitationally. Different from the daytime advection by prevailing wind, the turbulent mixing is very weak in nighttime seeping phenomena because of the stable atmospheric condition. In the west side, the cool air flows over the valley of moat (20m depth) and spreads out into the built-up area.In the east side, cool air front sometimes penetrates the adjacent CBD area and reach near the Tokyo Station. The wide streets have a larger effect on cool air seeping than the moat dose even though water temperature is higher than ambient air temperature.

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In order to 己valuate the mitigating effects of urban heat island l 〕 y wall greening ， an experiment to characterize the evaporation effect of a greening system and to quantify its heat balance was carried out ， At heat balance analysis， sensible heat flux is calculated using heat transfer coef 丘cient estimated by measurements with SAT （ Sol − air Temperamre ） meter ． As a result， it is confirmed that wall greening has the mitigating effects ofheat island due to the sensible heat reduction by consuming the latent heat by evapotranspiration 、 And it is able to evaluate the effects of wa 】 1 greening system using evaporation ef［ iciency as an index ofevapotranspiration ability ． 1． は じ め に