Dear Tom,
Large windmills generate electric power from the wind. If enough windmills are put into production, could they slow the wind and effect the weather?
—Jim Palador, Crown Point, Ind.
Dear Jim,
It is true that windmills remove energy from the atmosphere by tapping the kinetic energy of wind, but that same energy would otherwise be lost by friction with the ground. The wind begins losing energy to windmills a little above the surface rather than by friction right at ground level. It is the same with the wind blowing through trees or over buildings. In general, the lowest layer of the atmosphere from the surface up to about 1,500 feet is known as the friction layer, the layer in which winds are reduced because energy is being lost to friction with the ground.