Abstract
The vertical distribution of wind velocity in the shallow layer over the ground is represented empirically by the power law u∞zP for obtaining design wind pressure to the structure, where u is wind velocity at height z above the ground.
The power exponent p is specified only by the roughness of the ground under the strong wind. However, under moderate and slow wind, the power exponent also depends on the vertical difference of temperature of the air layer. The observations of wind profile have been made in the air layer up to 48 m above the ground at Kokubunji in the outskirts of Tokyo, and dependencies of the power exponent on time, wind velocity, temperature difference and stability of the air layer were obtained.
It seems to be rather advisable to use logarithmic wind profile than power wind profile for the study of transport and diffusion in the atmosphere. In this case, linear term of height is added as the correction for the stability. The profile, expressed as u=u∗k-1(ln z/zo+βL-1 •(z-z0)), where u*, zo and L are friction velocity, roughness length and stability length respectively, was derived from similarity hypothesis, and has been already assured to fit well results of observations in the lowest ten meters above the level grassy land. Following the logarithmic plus linear wind profile, our results have been analyzed and the profile seems to represent the observed wind velocity in the same degree as power profile does. Parameters of wind profile, u∗, zo and L, were calculated from the data and the comparision with the results of shallower layer was made.
