Investigations into observation data obtained at Tokyo tower using quantitative evaluation values for surface roughness of urban districts

At Tokyo Tower, wind observations have been carried out œntinuously at heights of 250m, 107m and 25m above the grand. In this paper, the authors have investigated the relationship between the vertical profile of the mean wind speed obtained from the data during a period of 1974 to 1996 and both the building area ratio and the ratio of an area for buildings with four or more stories to that for all buildings obtained from the dimensions of all structures on the windward side of the observation points. When fitting a power low profile to the observation results, the power law exponent ranging from 0.48 to 0.56 was obtained. However, when a zero-plane displacement was considered in the evaluation of the profile, the power law exponent became 0.38 to 0.48. These values correspond well both to the plane density of the windward area and the abovementioned ratio of the area of buildings for four or more stories.