air mass

American  

noun

1. a body of air covering a relatively wide area, exhibiting approximately uniform properties through any horizontal section.

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air mass British  

noun

1. a large body of air having characteristics of temperature, moisture, and pressure that are approximately uniform horizontally

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air mass Scientific  

1. 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.

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Etymology

Origin of air mass

First recorded in 1890–95

Example Sentences

The storm was expected to linger for days, shifting into the heavily populated mid-Atlantic and northeastern states while crippling daily life and ushering in a frigid air mass across the country.

From Barron's • Jan. 23, 2026

Organisers had warned him to cancel the 2015 open air mass in Tacloban as the weather had worsened.

From BBC • Apr. 22, 2025

The contrast between this extremely cold air mass and much milder air further south is going to "supercharge" the jet stream.

From BBC • Jan. 20, 2025

A relatively stable air mass blows from southwest to northeast over the Transverse Ranges north of L.A.

From Los Angeles Times • Jul. 19, 2024

Hubbard began to explain that a tropical air mass was moving in from— Groves cut Hubbard off.

From "Bomb" by Steve Sheinkin