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 vast Himalayan glaciers cool enormous air masses that slide downslope under gravity, creating what scientists call katabatic winds.

From Science Daily

But even when rain isn’t falling, Southern California will feel the effects of the moist air mass over the region.

From Los Angeles Times

As an island squeezed between the vast Atlantic Ocean and continental Europe, the UK sits at the intersection of a whole series of major air masses.

From BBC

The extreme weather, part of a bitterly cold air mass that has descended on the south and eastern US, is forecast to linger over the next couple of days.

From BBC

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

From BBC