Vertical coherence and phase delay between wind components in strong winds below 20 m

Abstract

Vertical coherence and phase delay between wind components in strong winds in the lowest 20 m over uniform terrain in New Zealand have been analysed. The vertical decay constants and slopes for the horizontal wind components could be described as linear functions of the ratio of vertical spacing to mean height (δz/z), with relatively little scatter. The decay constants for the lateral were smaller than for the longitudinal components, the slopes larger for the lateral components, as found previously. The coherence of vertical velocity is best described by exponential decay functions multiplied by a parameter which decreases linearly from 1 (for δz/z=0) to 0.5 (for δz/z=1). The decay constants increased linearly with δz/z, as in the case of the horizontal components. There were no significant phase differences for the vertical components. Lateral and vertical decay constants for the longitudinal wind component could be fitted to identical functions of δy/z and δz/z, respectively.