A qualitative term to describe a widespread body of air with approximately uniform
characteristics which had been identified at a given time over a particular region
of the earth's surface. Sometimes an air mass is marked by
inert tracers such as
SF6
which may be added to it.
The composition of a given air mass undergoes alteration as it migrates, chemical
changes occur, compounds are removed by dry and wet deposition and new impurities
are added to the mass.
Source:
PAC, 1990, 62, 2167
(Glossary of atmospheric chemistry terms (Recommendations 1990))
on page 2172