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Record 1 2003-04-09


Subject field(s)
  • Atmospheric Physics
  • Mathematical Geography

Either of two belts or regions near 30 degrees north or 30 degrees south; characterized by calms and light baffling winds.


Horse latitudes, two belts of latitude where winds are light and the weather is hot and dry. They are located mostly over the oceans, at about 30° lat. in each hemisphere, and have a north-south range of about 5° as they follow the seasonal migration of the sun. The horse latitudes are associated with the subtropical anticyclone and the large-scale descent of air from high-altitude currents moving toward the poles. After reaching the earth's surface, this air spreads toward the equator as part of the prevailing trade winds or toward the poles as part of the westerlies.


The term horse latitudes supposedly originates from the days when Spanish sailing vessels transported horses to the West Indies. Ships would often become becalmed in mid-ocean in this latitude, thus severely prolonging the voyage; the resulting water shortages would make it necessary for crews to throw their horses overboard.


The belt in the Northern Hemisphere is sometimes called the "calms of Cancer" and that in the Southern Hemisphere the "calms of Capricorn."

Key term(s)
  • horse latitudes
  • horse-latitudes
  • horse-latitude


  • Physique de l'atmosphère
  • Géographie mathématique

Ceintures de vents variables faibles et de beau temps associées aux anticyclones subtropicaux, approximativement entre les latitudes 30 et 35°.


À 30° de l'équateur, dans les deux hémisphères, on trouve la zone des calmes tropicaux ou «ceintures subtropicales», qui sont des zones de hautes pressions, où les vents sont faibles et variables.


Très caractéristiques sont les hautes pressions qui se localisent au nord du jet sur le Pacifique sud-oriental en avant de l'obstacle andin. On donnait autrefois à ces hautes pressions le nom de horse-latitude, vieux terme hérité de la marine à voile qui rappelait le temps où les vaisseaux restaient parfois immobilisés pendant plusieurs semaines dans les zones des calmes [...], on devait faute d'eau et de nourriture jeter à la mer les chevaux du bord.


Le «Vocabulaire météorologique international» (OMMV) utilise le terme «zone des calmes équatoriaux» pour désigner cette notion. Cependant, selon les sources consultées, la «zone des calmes équatoriaux» est une zone de basses pressions qui se situe approximativement entre le 10° de latitude Nord et 10° de latitude Sud.

Key term(s)
  • ceintures subtropicales
  • hautes pressions subtropicales
  • hautes pressions


Campo(s) temático(s)
  • Física de la atmósfera
  • Geografía matemática

latitudes de calmas ecuatoriales: Zonas de buen tiempo asociadas con los anticiclones subtropicales, situadas entre los 30° y los 35° de latitud, donde predominan vientos flojos y variables.

Key term(s)
  • latitudes de calmas ecuatoriales
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