Buys Ballot's law

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With the wind to one's back (Note: person in figure is facing you), a low-pressure center (L) will be to one's left, high pressure (H) to one's right (in the Northern Hemisphere)

In meteorology, Buys Ballot's law may be expressed as follows: In the Northern Hemisphere, stand with your back to the wind; the low pressure area will be on your left. This is because wind travels counterclockwise around low pressure zones in the Northern Hemisphere. It is approximately true in the higher latitudes of the Northern Hemisphere, and is reversed in the Southern Hemisphere, but the angle between the pressure gradient force and wind is not a right angle in low latitudes. See Coriolis effect#Flow around a low-pressure area.

This rule, which was first deduced by the American meteorologists J.H. Coffin and William Ferrel, is a direct consequence of Ferrel's law. The law takes its name from C. H. D. Buys Ballot, a Dutch meteorologist, who published it in the Comptes Rendus, November 1857. While William Ferrel theorized this first in 1856, Buys-Ballot was the first to provide an empirical validation.

[edit] External links

M. Buys Ballot, "Note sur le rapport de l'intensite et de la direction du vent avec les ecarts simultanes du barometre", Comptes Rendus, Vol. 45 (1857), pp. 765–768.

This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.