Displacement height

The displacement height (or zero plane displacement height) of a vegetated surface—usually indicated with d—is the height at which the wind speed would go to zero if the logarithmic wind profile was maintained from the outer flow all the way down to the surface (that is, in the absence of the vegetation). In other words, it is the distance above the ground at which a non-vegetated surface should be placed to provide a logarithmic wind field equal to observed one. By another point of view, it should be regarded as the level at which the mean drag on the surface appears to act (Jackson, 1981). For forest canopies, it is estimated to vary between 0.6 and 0.8 times the height of the canopy (Arya, 1998; Stull, 1988).

If not entered explicitly, EddyPro computes the displacement height as: