Some Observation of the Wind over the City

Abstract

The vertical distribution of mean wind velocity and fluctuation was observed at several places in Tôkyô, using Robinson small cup anemometers, Nakaasa type wind vane and other vane which rotates around the horizontal axis. We observed the fluctuation in the velocity and the angle of inclination of the vane at every 5 seconds.
The results are as follows : 1. Vertical distribution of mean velocity fits to the logarithmic law,
u = (u^∗/k) l_n ((Z-d) / Z₀).
where u, u^∗, Z₀, d and k denote the velocity at height Z, the friction velocity, the roughness parameter, the zero plane displacement and Kármán’s constant, respectively.
2. Frequency distribution of turbulence components is approximately normal Gaussian distribution except vertical component.
3. Correlation between the wind velocity and the angle of inclination of the vane in the vertical direction is small.
4. When the vane directs downward its continuing time is long and the wind velocity is large. But when the vane directs upward the continuing time is shorter and the velocity is smaller.