A system used to identify and to characterize the different air masses
according to a basic scheme.
A number of systems have been proposed, but the Bergeron classification
has been the most widely accepted. In this system, air masses are designated first according to the thermal
properties of their source regions: tropical
(P); and less frequently, arctic
(A). For characterizing the moisture distribution, air masses are distinguished as to continental
(c) and maritime
(m) source regions. Further classification according to whether the air is cold (k) or warm (w) relative to the surface over which it is moving indicates the low-level stability
conditions of the air, the type of modification from below, and is also related to the weather occurring within the air mass. This outline of classification yields the following identifiers for air masses: cTk, cTw, mTk, mTw, cPk, cPw, mPk, mPw, cAk, mAk, mAw; the last of which is never used. H. C. Willett, in his classification, introduces further distinction between stable (s) and unstable (u) conditions in upper levels. Some authors may include equatorial
(M), or superior air
(S) in their classifications. Others prefer to omit the arctic (A) type and describe all air masses on the basis of polar and tropical air, separated by the polar front
Byers, H. R. 1944. General Meteorology. p. 247.
Hewson, E. W., and R. W. Longley 1944. Meteorology, Theoretical and Applied. p. 249.
Willett, H. C. 1944. Descriptive Meteorology. 183–191.
Palmén, E. 1951. Compendium of Meteorology. 599–620.
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact firstname.lastname@example.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.