Griggs - Putnam Wind Energy Index
The Griggs-Putnam Index is one of several empirical methods of estimating the prevailing wind speed at a site by observing the growth patterns of trees. Strong winds will deform trees and shrubs so that they indicate an integrated record of the local wind speeds during their lives. The effect shows up best on coniferous evergreens because their appearance to the wind remains relatively constant during the year. Deciduous trees shed their leaves in the winter and thus change the exposed area tremendously. If average wind speed is high but still below some critical value, above which deciduous trees cannot survive, they will not indicate relative differences in wind speeds very well, although they do show distinctive wind damage.
