Abstract
The wind is observed at the lower part in a built-up area. The measuring site is located at Minato-ku Tokyo, Japan. Seven anemometers are arranged at several heights, from 6m to 46m. The observation began in Aug., 1972, and will continue to May, 1976. Here the results of the survey in the first one year are described. A high rise building is under construction in the center of the measuring site. It is intended to clarify the influences of the tall building on the air flow in the streets. The main results are as follows. 1) The prevailing wind direction is NNW or SSE〜SSW at the height of 46m. As for only the strong wind, south direction is most frequent. 2) The longest time length during which the calm continues is 14hr. at Point No. 1 (z=46m), but that value becomes 170hr. at Point No. 4 (z=6m). The longest time length during which the strong wind continues is 11hr. at Point No. 1, but it is not observed at Point No. 4 that the strong wind continues for one hour. Here "calm" is defined as the conditions during which the 60-min. mean wind velocity is lower than 2m/s, and the strong wind is defined as the condition during which the 60-min. mean wind velocity exceeds 10m/s. 3) The percentage of the days on which V (24-hr. Max) exceeds 10m/s is 68% at Point No. 1, 19% at Point No. 3 (Z=4m), 26% at Point No. 4 (Z=6m) and 7% at Point No. 7 (Z=4m). 4) The distribution of the gust factor with the height, at the lower part in the built-up area, is expressed as below. <G.F.>^^^-=2.95Z^<-0.16> where 6≦Z<300.
