On the Structure of Wind near the Ground (II)

Abstract

The gustiness of wind is one of the most effective representative of the state of wind. But it depends on the method and instrument of observation. Generally, it is thought that the fluctuation of wind velocity is caused by the eddies in the wind. Then the gustiness of wind relates to the range of the observable eddies, which is limited by the duration of observation and the sensibility of instrument. The duration of observation regulates the effective largest eddy, and the sensibility of instrument regulates the effective smallest eddy. The negative five-thirds power law of eddy spectrum is assumed to be applicable to these eddies. Then the relation between the duration T and the gustiness is obtained as follows:
These results are ascertained by the comparison with practical observation. The influence of the sensibility of instrument is also estimated.