FIELD MEASUREMENTS ON THE COOLING EFFECT OF THE IMPERIAL PALACE AND ITS THERMAL INFLUENCE ON THE SURROUNDING BUILT UP AREA

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.