  The wind energy community is gradually recognizing the significance of
atmospheric stability in both power production and structural loading. However,
estimating stability requires temperature gradient data which are not commonly
measured by the wind farm developers or operators. To circumvent this problem,
we propose a simple approach \emph{\'{a} la} Swinbank, to estimate stability
from only three levels of wind speed measurements. As such, this approach is
ideally suited for sodar and lidar--based wind measurements owing to their high
vertical resolution in the surface layer.
