Wind atmosphere based upon how far clouds move from one image to the next. Wind engineering describes the study of the effects of the wind on the built environment, including buildings, bridges and other man-made objects. Historically, the Beaufort wind force scale (created by Beaufort) provides an empirical description of wind speed based on observed sea conditions. Originally it was a 13-level scale, but during the 1940s, the scale was expanded to 17 levels. There are general terms that differentiate winds of different average speeds such as a breeze, a gale, a storm, tornado, or a hurricane. Within the Beaufort scale,
Wind power in the United States in power output from wind farms, which poses difficulties incorporating wind power into an integrated power system. Wind turbines are driven by boundary layer winds, those that occur near the surface of the earth, at around 300 feet. Boundary layer winds are controlled by wind in the higher free atmosphere and have turbulence due to interaction with surface features such as trees, hills, and buildings. Short term or high frequency variations are due to this turbulence in the boundary layer. Long term variations are due to the passage of transient waves in the atmosphere, with a characteristic time scale of