polar front

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polar front, zone of transition between polar and tropical air masses. Its average position during the winter is at about 30° lat. and during the summer at about 60° lat. In the N Atlantic Ocean, for example, the polar front can often be traced as a continuous line extending over thousands of miles, usually toward the northeast from a point just off the coast of the United States at about 30°N. Most cyclones outside the tropics develop along the polar front from waves caused by the juxtaposition of cold air moving toward the equator and hot air moving toward the poles; the earth's rotation gives this air its cyclonic twist. See front.

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polar front The main boundary line between polar and tropical air masses along which depressions develop in mid latitudes, especially over the oceans. The front is in general displaced towards the equator in winter and the poles in summer, though large displacements in either direction take place over shorter periods in individual sectors of the hemisphere.

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polar front The main boundary line between polar and tropical air masses along which depressions develop in mid latitudes, especially over the oceans. The front is in general displaced equatorwards in winter and polewards in summer, though large displacements in either direction take place over shorter periods in individual sectors of the hemisphere.