Fig. 1 Source regions of
air masses in relation to the
polar front and the
intertropical convergence
zone (ITC). From Elements
of Physical Geography, 4th
ed., by Arthur N. Strahler
and Alan H. Strahler, p.
125. Copyright (c) 1989 by
John Wiley & Sons, Inc.;
reproduced with
permission
Table 1 Properties of air masses
a
Major group
Subgroup
Source region
Properties of
source
Polar (including
arctic)
Polar continental
(cP)
Arctic Basin; northern Eurasia and northern North
America; Antarctica
Cold, dry, very
stable
Polar maritime
(mP)
Oceans poleward of 40 or 50
Cool, moist,
unstable
Tropical (including
equatorial)
Tropical
continental (cT)
Low-latitude deserts, especially Sahara and
Australian Deserts
Hot, very dry,
stable
Tropical
maritime (mT)
Oceans of tropics and subtropics instability toward
west side of ocean
Warm, moist,
greater
a
From Trewartha et al. (1967)
142
Appendix A: Air Masses and Frontal Zones