atmosphere vs air mass

atmosphere and air mass both are nouns.

Word	Noun	Adjective	Verb	Adverb
atmosphere	Yes	No	No	No
air mass	Yes	No	No	No

As nouns, air mass is a hyponym of atmosphere; that is, air mass is a word with a more specific, narrower meaning than atmosphere:

Other hyponyms of atmosphere include anticyclone, cyclone, fog, fogginess, murk, murkiness.

atmosphere (noun)	air mass (noun)
a distinctive but intangible quality surrounding a person or thing	a large body of air with uniform characteristics horizontally
the mass of air surrounding the Earth
the envelope of gases surrounding any celestial body
a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade
the weather or climate at some place
a particular environment or surrounding influence