On the Structure of Wind near the Ground (V)

Abstract

In order to explain the connection between the horizontal and vertical structures of wind, the concept of the coupling eddy is postulated. The coupling eddy in the vertical structure is coincident with the vertical largest eddy. The movements of the coupling eddy in the horizontal and vertical directions are thought to be completely correlated with each other, and the correlation coefficient between two velocities u_* and w_* of the coupling eddy is assumed to be given by the following relation
The turbulent velocities u and w which are observed in the wind contain not only the components of coupling eddy but also many components of eddies of other ranks, The correlation coefficient R_uw between u and w can be related with Ru_*w*.
For the natural wind, the effective largest eddy in horizontal plane usually increases its scale simultaneously with the increase in the time duration T of observation. Thus, as the time duration is prolonged, R_uw decreases in the following relation
This relation is examined by the practical observation.