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air mass

noun
1.
a body of air covering a relatively wide area, exhibiting approximately uniform properties through any horizontal section.
Origin
1890-1895
1890-95
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for air mass

air mass

noun
1.
a large body of air having characteristics of temperature, moisture, and pressure that are approximately uniform horizontally
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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air mass in Science
air mass  
A widespread body of air that originates over a large area of land or ocean and assumes the temperature and humidity of that area, with characteristics distributed fairly evenly throughout the horizontal layers of the mass. Air that stands over the Caribbean Sea, for example, becomes a warm, humid maritime tropical air mass, while air that lies in the Arctic regions of northern Canada takes on the cold and dry characteristics of its surroundings and becomes a continental polar air mass. When air masses of differing properties come into contact in the middle latitudes, they frequently generate storm fronts.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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