Beaufort wind scale

A system of estimating and reporting wind speeds using a numerical scale ranging from 0 (calm) to 12 (hurricane).

It was invented in the early nineteenth century by Admiral Beaufort of the British Navy and was originally based on the effects of various wind speeds on the amount of canvas that a full- rigged frigate of the period could carry. It has since been modified and modernized and in its present form for international meteorological use it equates 1) Beaufort force (or Beaufort number), 2) wind speed, 3) descriptive term, and 4) visible effects upon land objects or sea surface. One land adaptation is the NRM wind scale.
U.S. Weather Bureau 1955. Circular N. 7th ed., . p. 100.
U.S. Weather Bureau 1954. Circular M. 9th ed, . p. 14.
Byers, H. R. 1944. General Meteorology. 83–85.
Donn, W. L. 1951. Meteorology with Marine Applications. 132–135.
List, R. J., ed. 1951. Smithsonian Meteorological Tables. 6th rev. ed., . p. 119.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.

1. The study of the physics, chemistry, and dynamics of the earth's atmosphere, including the related effects at the air–earth boundary over both land and the oceans. Fundamental topics include the composition, structure, and motion of the atmosphere. The goals ascribed to meteorology are the complete understanding and accurate prediction of atmospheric phenomena.