A term and calculation used to describe how wind speed increases with height above the surface of the earth. The degree of wind shear is a factor of the complexity of the terrain as well as the actual heights measured. Wind shear increases as friction between the wind and the ground becomes greater. Wind shear is not a measure of the wind speed at a site. It is an extrapolation of the difference in wind speed between two different heights above the ground. Thus, high wind shear at a site does not necessarily mean high wind speeds at the site.