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Air Masses and Fronts

Source Regions, Classification, Properties Of Air Masses, Fronts, Cold Fronts, Warm FrontsStationary fronts

An air mass is an extensive body of air that has a relatively homogeneous temperature and moisture content over a significant altitude. Air masses typically cover areas of a few hundred, thousand, or million square kilometers. A front is the boundary at which two air masses of different temperature and moisture content meet. The role of air masses and fronts in the development of weather systems was first appreciated by the Norwegian father and son team of Vilhelm and Jacob Bjerknes in the 1920s. Today, these two phenomena are still studied intensively as predictors of future weather patterns.

In some instances, the collision of two air masses results in a stand-off. Neither mass is strong enough to displace the other, and essentially no movement occurs. The boundary between the air masses in this case is known as a stationary air mass and is designated on a weather map by a solid line with triangles and half circles on opposite sides of the line. Stationary fronts are often accompanied by fair, clear weather, although some light precipitation may occur.



Ahrens, C. Donald. Meteorology Today. 2nd ed. St. Paul, MN: West Publishing Company, 1985.

Eagleman, Joe R. Meteorology: The Atmosphere in Action. 2nd ed. Belmont, CA: Wadsworth Publishing Company, 1985.

Lutgens, Frederick K., and Edward J. Tarbuck. The Atmosphere: An Introduction to Meteorology. 4th ed. Englewood Cliffs, NJ: Prentice Hall, 1989.

Lutgens, Frederick K., Edward J. Tarbuck, and Dennis Tasa. The Atmosphere: An Intorduction to Meteorology. 8th ed. New York: Prentice-Hall, 2000.

Moran, Joseph M., and Michael D. Morgan. Essentials of Atmosphere and Weather. New York: Macmillan Publishing Company, 1994.


"Genesis of Fronts and Airmasses." Weatherwise (December 1985): 324-328.

David E. Newton


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—Referring to an area of high pressure around which winds blow in a clockwise direction in the northern hemisphere.


—Referring to very large land masses.


—Referring to an area of low pressure around which winds blow in a counter-clockwise direction in the northern hemisphere.


—The amount of water vapor contained in the air.


—Referring to the oceans.


—Referring to the surface features of an area.

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